Over the recent years, there have been an increased number of entry-and-exit systems (entry-and-exit management systems) contrived to permit only a limited number of persons (privileged persons) to enter a predetermined room (security room) by unlocking a door through an authenticating operation. This entry-and-exit system has, however, such a tailgating problem that when a regular user is authenticated and opens the door, a suspicious person is enabled to enter the security room in a way that follows the authenticated regular user. On the other hand, as a solution of this tailgating problem, there is an entry-and-exit system which grasps an authentication status of a person existing in front of the door and detects, when an unauthenticated person passes through the door, this person as an invalid passer.